Kinematic Power Corrections in Off-Forward Hard Reactions

We develop a general approach to the calculation of kinematic corrections proportional to t/Q(2), m(2)/Q(2) in hard processes which involve momentum transfer from the initial to the final hadron state. As the principal result, the complete expression is derived for the time-ordered product of two electromagnetic currents that includes all kinematic corrections to twist-four accuracy. The results are immediately applicable, e. g., to the studies of deeply virtual Compton scattering.